I recently purchased a '95 X306 which had a very rough idle. Raising the RPM slowly it seemed to smooth out, but would crap out above 3k. I did a compression test by first pulling the fuel pump fuse and began from the front changing spark plugs (NGK Patinums) and boots as I went from front to back, also checking the coils as I went. The coils were between 1.5 - 1.8 ohms and compression between 120 and 150 psi. Fired right up and ran smooth after that. So I drove it to the part store to get a battery and some R134a. It ran fine around town (25MPH speed limit), so I decided to see how it ran on the freeway. Taking it easy, it was fine to the 65MPH speed limit, but when I "punched it" it fell flat. After that it would run smoothly at the lower RPM's, So I checked the fuel pressure at the rail and got the 53psi and still at the upper RPM's it cuts out. So I took the primary fuel pump relay out and bypassed the secondary relay and retested and got 37psi. My questions are, is the secondary pump pressure within spec, or do both fuel pumps have to be at the same psi rating? And what else could cause this symptom.

 

The fuel pressure regulator will keep the fuel pressure at 43 PSI at idle and climbs to 46 at higher engine RPMs ( intake vacuum controlled )

This will be the case with both fuel pumps running

The second fuel pump will not come on until 4000 RPM and drop out at 3000 as it passes back through 4000

 

See page 64 , end of paragraph

http://jagrepair.com/images/Training...20-%202000.pdf

 

Thank you!!! That is alot of GREAT information.

 

See this tread for more info

https://www.jaguarforums.com/forum/x...manual-253724/

 

The supercharger drive belt is ok? Any leaks in the supercharger boost pipes?

 

Do you know if the ECU is going from open loop to close loop by the coolant temp going above 88 degree C ?

The instrument gauge uses a different sensor then the ECU

TPS reading 0.60 volts DC at idle on the center Green / Yellow wire and no open spots on the TPS sweep , the TPS connector needs to stay on

MAF reading 1.2 volts DC at idle on the Green / Pink wire

See page 63

http://jagrepair.com/images/AutoRepa.../jagxj1996.pdf

You will be using NAS or North American Specification

Crankshart Position sensor face of the sensor clean as well as the connector ? CEL code P0335

, your timing may not be advancing or retarding

Inspect the ECU connectors for no corrosion

There are 2 relays you can swap around

 

Ugh!! New air pump and check valve, new o2 sensors, New fuel pressure relief valve. Maf specs out and tps, ckps, cmps all function before 88c and it goes into closed loop. Once in closed loop it will only rev to 2500 rpm then starts to misfire and worsens at higher rpms. I still can't think of anything else. Runs and revs beautifully when cold....

 

someone found the crankshaft position sensor had grime on the face of the sensor that became more prone to not reading the signal at higher RPMs

in the wire harness as it passes over the fuel rail there is a splice that may be damaged from corrosion

This would be the signal protection of the sheild ground

This would be the X color wire

 

I replaced the cat and found an o2 sensor fried much like one I replaced earlier. Will run up to speed but still has miss fire starting at 2300 and gets bad at 3300.

Cat from Welsh

Fried O2

Bad cat

 

Looks like melting , correct ?

I have more info but WiFi going in and out

There is a cheaper O2 sensor that is connector ready Bosch # 13789

https://www.autozone.com/engine-mana...789/491474_0_0

The crush washer if not present and important for correct reading is a 12 mm thread not the same as the X300 spark plug but can be obtained from a cheap autolite copper plug I have the # for in the garage

The sensor is the same for all 4 positions

Now would be the time for donut gaskets replacement and manifold crack inspection

Vee gave me the # and it works but the # is in the garage somewhere

See page 80

http://jagrepair.com/images/Training...20-%202000.pdf

The O2 sensors are a different titanium base technology and they operate and read differently

 

What was the part # you used at Welsh for a 4 sensor X300 ?

Europe has 2 or 4

 

The number for the cat I got from Welsh ent. is NBD6711CA, it has four O2 sensor bungs and is for the "spherical" union at the bottom (nobody mentioned that ). I did use new gaskets at the manifold. I found out that the "olive" for the bottom is made out of stainless so I reused it, saving $40+. The O2 sensors I replaced with the Bosch units earlier. I had "cleared" the codes and took it out for a test ride, hence my previous complaint that I didn't instantly have results. I paid the $80 for 1/2 a tank so as to have a full tank and added some fuel injection cleaner. I continued to drive it and have been getting better results. Today I experienced a jolt at the seat indicating things are getting better. I've yet to "Punch It!" to see what happens for fear of undoing the time spent trying to fit my arms around every sharp object under the hood. Thank you Parker7 ( Okay, everyone...) and your infinite source of information. More to come...

 

I heard that

Thinking

2nd fuel pump running ? and might consider jumpering the relay sockets to run 2nd pump at all times

This may produce a over fuel condition ( double pumps should not be on until 4000 RPM ) so you would remove the # 1 fuel pump relay and observe

This will not be a 2 fuel pump capacity but this switching fuel pumps should be a observable same as with only a # 1 fuel pump running

So we are looking at the # 2 fuel pump control and the fuel pump rotating as separate things

EGR _Error signal at target value of 0 at point of acceleration , I think the EGR should go back closed at this point

 

I jump the second pump early on and it works. What I noticed is a missfire at 2300 and again at 3500. That isn't happening anymore. Since the car came from a moisture area I'm thinking it might have been water in the gas. It definitely is running better but I'm still testing. I'll check for doc's after the 200 mile mark( ACI [ after cat installation] ).

 

There was someone that had grime on the face of the CKPS that degraded the signal at high RPMs

This because the CKPS signal is compressed along the time axis and the ECU could not disern it well

There was someone who broke off a extra missing tooth on the CKPS ring gear completely confusing the ECU

The 2 wires of the CKPS are shielded with a ground stud on the rear firewall to protect the CKPS signal from being corrupted ( in this spesific example we are looking at 2 competing AC like signals in the same wire )

The coils can add " Bad Electricity " into car from arcing on the coil well walls and ensuring the large woven ground strap from the starter mount bolt to the car frame can help solve unlogical problems

The coil well walls on the valve cover are electrically isolated in theory by the plastic shoulder bushings on the 13 or so mount bolts but.............

You ECU wants only to be powered by smooth DC power but a stray AC signal can be present on a wire at the same time like in a vacuum tube guitar amplifier

The large ground strap is best gotten to from the bottom with either a 13 or 15 mm socket

The should also be a deducted ground strap on the ECU mount bolt

The engine and transmission ECU cross talk to each other as they dance together and the transmission connector on the transmission body can cause the engine to hesitate but this usually only accurse in the park to first RPM range in the driveway

 

The Mass Air Sensor on the supercharged engine is different then that used on the normally asperated and has been missed before

To know that it is at least alive it will read 1.2 volts DC on the middle wire of the connector at the proper idle speed

Vee had a suggestion to put a slight twist on the pins / blades to ensure connections

The TPS will read 0.60 volts DC at the idle stop on its middle wire , both these readings will be with heir connector remaining installed

What I found with mine was the TPS connector was not locked on

If there is an open spot on the TPS range the ECU will reject the signal and revert to a less then optimal set of maps minus a TPS

This takes time for this to accure and once the TPS signal comes back in a reasonable range the ECU will come back to the optimal set of maps

This again takes some time to switch back

this may explain your middle range anomaly

 

OK!!! so far so good !! car is running sweet!! Catalytics finally did the trick.....now on to the next series of thing to do, u joints, center support bearing. control arm bushings and ball joints, and most likely, traction control reluctors!!!
Thanks every one!!!